Thèses sur le sujet « Dipolar systems »
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Sutcliffe, Oliver Brook. « New extended dipolar systems ». Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366511.
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McGrother, Simon C. « Phase transitions in dipolar and associating systems ». Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389929.
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Fedorov, Aleksey. « Non-conventional Many-body Phases in Ultracold Dipolar Systems ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS580/document.
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Le problème de la détection et de ladescription des nouveaux états quantiquesmacroscopiques, caractérisées par des propriétésexotiques et non-conventionnelles, estd’importance fondamentale dans la physiquemoderne. Ces états offrent des perspectivesfascinantes dans le domaine de traitementd’information, de simulations quantiques et derecherche des nouveaux types des matériaux.Dans ce travail de thèse nous développons unethéorie qui permet de décrire des phases non conventionnellesdans des systèmes des gazultra-froids dipolaires. Ces systèmes sontactivement étudiés expérimentalement enutilisant des atomes à grand-spins, desmolécules polaires et des excitations dipolairesdans des semi-conducteurs. Nous mettonsl'accent sur la révélation du rôle de l’interactiondipôle-dipôle à long porté.Nous considérons l’effet de rotonization dansun système de gaz des bosons dipolaires «tiltés»aux interactions faibles dans une couchehomogène. Nous prédisons l’effet derotonization pour un gaz de Bose faiblementcorrélé des excitons dipolaires dans une couchede semi-conducteur et nous calculons lediagramme de stabilité. Ensuite, nousconsidérons des superfluides d’onde-p desfermions identiques dans des réseaux 2D.Finalement, nous faisons une discussion sur unautre état superfluide intéressant des moléculespolaires fermioniques, qui devrait apparaitredans des systèmes bicouchesThe problem of revealing anddescribing novel macroscopic quantum statescharacter- ized by exotic and non-conventionalproperties is of fundamental importance formodern physics. Such states offer fascinatingprospects for potential applications in quantumin- formation processing, quantum simulation,and material research. In the present Thesis wedevelop a theory for describing nonconventionalphases of ultracold dipolar gases.The related systems of large-spin atoms, polarmolecules, and dipolar excitons in semiconductorsare actively studied in experiments.We put the main emphasis on revealing the roleof the long-range character of the dipole-dipoleinteraction.We consider the effect of rotonization for a 2Dweakly interacting gas of tilted dipolar bosonsin a homogeneous layer. We predict the effectof rotonization for a weakly correlated Bosegas of dipolar excitons in a semiconductorlayer and calculate the stability diagram. Wethen consider p-wave superfluids of identicalfermions in 2D lattices. Finally, we discussanother interesting novel superfluid offermionic polar molecules
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Spiteri, Ludovic. « Self-assembly of dipolar particles ». Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0261/document.
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Cette thèse couvre l'auto-assemblage de particules dipolaires (magnétiques/électriques). Ces systèmes sont abondants en physique de la matière condensée (molécules et nanoparticules magnétiques, particules colloïdales magnétiques, bactérie magnétotactique, etc.). Sur un plan fondamental, ils représentent un défi important en raison de l'anisotropie et de la longue portée de l'interaction de paire. Le principal objectif de ce travail de recherche est de prédire les microstructures de ces systèmes en tenant compte de façon adéquate de l'interaction complexe dipôle-dipôle ainsi que des effets stériques et ceux dus à un éventuel confinement. Comprendre et revisiter les interactions de filaments dipolaires tels que des aiguilles et des chaînes faites de billes dipolaires est une première étape importante de cette thèse. En effet, les chaînes sont les constituants élémentaires de nombreux systèmes dipolaires, notamment sous l'effet d'un champ magnétique extérieur appliqué. Ensuite, l'agrégation colonnaire des chaînes dipolaires est examinée, ce qui conduit aussi naturellement à l'étude des cristaux dipolaires massifs où une nouvelle phase est découverte. Le cas plus générique des chaînes hélicoïdales est discuté en considérant les situations limites que sont les chaînes linéaires droites et en zigzag. L'association des chaînes dipolaires, dans le cas bidimensionnel, forme des rubans, puis une monocouche avec un réseau hexagonal. La réponse non triviale d'un tel réseau à un champ magnétique perpendiculaire imposé est aussi étudiée. Il est démontré qu'un réseau rhombique peut être induit de cette façon. Finalement, la sédimentation de particules paramagnétiques dans une monocouche inclinée en présence d'un champ magnétique est explorée via une étude mêlant expériences, théorie et simulations. L'ordre induit par gravité s'avère être une voie prometteuse pour l'élaboration contrôlée de réseaux bidimensionnelsThis thesis covers the self-assembly of dipolar (magnetic/dielectric) particles. These systems are abundant in condensed matter physics (magnetic molecules and nanoparticles, magnetic colloidal particles, magnetotactic bacteria, etc). They also represent a fundamental challenge owing to the both long range and anisotropic nature of the pair interaction. The main objective of this research work is to predict the microstructures of these systems by properly handling the intricate dipole-dipole interaction combined with steric and possibly confinement effects. Understanding and revisiting the interaction of dipolar filaments such as needles or chains made up of dipolar beads is a first important achievement in this thesis. Indeed, the chains are the fundamental building blocks of many dipolar systems especially under applied external magnetic field. Then, the columnar aggregation of dipolar chains is investigated which naturally leads to the study of the bulk dipolar crystals. A new phase is discovered there. The more generic case of helical chains is discussed by considering limiting situations such as straight linear chains and zigzag chains. The association of dipolar chains in two-dimensions forms ribbons then a monolayer with triangular lattice symmetry. The interesting response of such a layer to an imposed perpendicular magnetic is addressed as well. It is demonstrated that rhombicity can be induced that way. Finally, sedimenting paramagnetic particles in a tilted monolayer in presence of a magnetic field are investigated by experiments, theory and simulations. The gravity-mediated ordering is found to be a promising route to elaborate tailored two-dimensional patterns
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Guo, Zhenrong. « Characterization of ionic, dipolar and molecular mobility in polymer systems ». W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539623474.
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Changes in the ionic and dipolar molecular mobility in a polymer system are the basis for the changes in the dielectric mechanical properties of polymer materials. Frequency Dependent Dielectric Measurements (FDEMS) and Ion Time-of-Flight (ITOF) are two important techniques to investigate ionic and dipolar molecular mobility in polymer systems. The results can be related to the macro- and molecular dielectric, electrical and dynamic properties of polymeric materials. The combination of these two methods provides a full view of electric, dielectric and dynamic behavior for the systems as they undergo chemical and/or physical changes during polymerization crystallization, vitrification, and/or phase separation.;The research on microscopic mass mobility in polymer systems was done on three aspects: (1) ion mobility in an epoxy-amine reaction system; (2) dipolar mobility and relaxation during dimethacrylate resin cure and (3) dye molecule migration and diffusion in polymer films.;In the ion mobility study, we separately monitor the changes in the ion mobility and the number of charge carriers during the epoxy-amine polymerization with FDEMS and ITOF measurements. The isolation of the number of carriers and their mobility allows significant improvement in monitoring changes in the state and structure of a material as it cures.;For the dipolar mobility and relaxation study, FDEMS measurements were used to detect structural evolution and spatial heterogeneity formation during the polymerization process of dimethacrylate resins. The dielectric spectra, glass transition (Tg) profiles and dynamic mechanical measurements were used to investigate the existence of two cooperative regions of sufficient size to create two alpha-relaxation processes representing oligomer rich and polymer microgel regions during the polymerization.;For the dye migration research, we tried to develop a visually color changing paper (VCP) due to dye molecule migration in polymer films. The mobility of dye molecules in polyvinyl films was controlled by the acidity of the environment. Ionamine derivatives of dyes were stable when mixed with acid. their diffusion in polymer films can be quickly triggered as the result of an acid/base neutralization reaction. The effect of the type of base, acid and the compatibility of polymer films on the diffusion rate is discussed.
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Sauerwein, Andrea C. « Estimations of dipolar couplings in multiple-spin systems by solid state NMR ». Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/191325/.
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Armstrong, William Paul. « Biological and mechanistic aspects of 1,3-dipolar cycloadditions of X=Y-ZH systems ». Thesis, Queen's University Belfast, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317050.
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Cartarius, Florian [Verfasser], et Giovanna [Akademischer Betreuer] Morigi. « Classical and quantum phases of low-dimensional dipolar systems / Florian Cartarius ; Betreuer : Giovanna Morigi ». Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2016. http://d-nb.info/1116344602/34.
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Brown, Scott Michael. « Using neclear magnetic resonance and the dipolar field to study structural properties of two-phase liquid systems ». Springfield, Va. : Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA395312.
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Burns, Teresa Ellen. « Asymmetric Adsorbate and Substrate Interactions in Physisorbed Systems : N2 on Graphite and Dipolar Molecules on Ionic Substrates ». DigitalCommons@USU, 1994. https://digitalcommons.usu.edu/etd/2090.
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Asymmetries in physisorbed systems give rise to interesting phases and phase transitions in two-dimensional (2D) monolayer and multilayer systems. The effects of asymmetric adsorbate and substrate interactions in monolayers of dipolar molecules on ionic substrates and N2 on graphite are studied.
In the case of dipolar molecules on ionic substrates, 2D dielectric phase transitions using a modified Blume-Emery-Griffiths (BEG) model are determined theoretically. A dipole adsorbed vertically above a metal ion lattice site, and pointing up (down), is assigned a spin s=+1 (s=-1). An empty lattice site is assigned a spin S=0. Analytic solutions for both ferroelectrically and antiferroelectrically ordered systems are found. The model is applied to CO adsorbed on MgO and NaCl, and preliminary results for the phase diagram of CH3F on NaCl, are presented.
Multilayer phase transitions for N2 on graphite are studied experimentally using synchrotron x-ray diffraction. The system is measured to undergo layering transitions, where the number of layers increases as the temperature of the system increases. A new multilayer phase diagram based on our results and the combined results published by other researchers is presented. The effects of capillary condensation on this multilayer system are quantified, and it is determined that its primary effect is to broaden the discrete layering transitions. The results for both studies are put into context with other adsorption systems with asymmetric interactions.
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Hurley, Margaret M. « Analysis of the dipolar lattice gas as a model for self-assembly in 1 and 2-dimensional systems / ». The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487780393265179.
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Kamm, Philipp Willi. « Understanding of lambda-orthogonal photo-induced reaction systems ». Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/234293/1/Philipp%20Willi_Kamm_Thesis.pdf.
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Using light as an energy source allows chemical reactions to be carried out with high precision in time and space. In time, because light can be switched on and off, in space, because light can be highly focussed. Further, different colours of light can be used to activate different reactants individually, even when they are present in the same reaction mixture. Herein, a system of two light-sensitive molecules was developed, which react completely sequence-independently with UV or visible light. The wavelength-dependence as well as the influence of chemical-physical parameters on such reactions were investigated in-depth.
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Valente, Angelo. « Isoxazolidines and oxazines : preliminary studies for the synthesis of N,O-heterocyclic systems via an organocatalyzed 1,3-Dipolar Cycloaddiction and a tandem reaction mediated by TEMPO salts ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4363/.
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This thesis is the result of the study of two reactions leading to the formation of important heterocyclic compounds of potential pharmaceutical interest. The first study concerns the reaction of (1,3)-dipolar cycloaddition between nitrones and activated olefins by hydrogen bond catalysis of thioureas derivatives leading to the formation of a five-membered cyclic adducts, an interesting and strategic synthetic intermediate, for the synthesis of benzoazepine. The second project wants to explore the direct oxidative C(sp3)-H α-alkylation of simple amides with subsequent addition of an olefin and cyclization in order to obtain the corresponding oxazine. Both reactions are still under development.
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Rumpel, Sigrun. « Protein NMR studies of two systems involved in bacterial pathogenicity ». Doctoral thesis, [S.l.] : [s.n.], 2006. http://webdoc.sub.gwdg.de/diss/2006/rumpel.
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List, Nanna Holmgaard. « Theoretical Description of Electronic Transitions in Large Molecular Systems in the Optical and X-Ray Regions ». Doctoral thesis, Department of Physics, Chemistry and Biology, University of Southern Denmark, Denmark, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201156.
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The size and conformational complexity of proteins and other large systems represent major challenges for today's methods of quantum chemistry.This thesis is centered around the development of new computational tools to gain molecular-level insight into electronic transitions in such systems. To meet this challenge, we focus on the polarizable embedding (PE) model, which takes advantage of the fact that many electronic transitions are localized to a smaller part of the entire system.This motivates a partitioning of the large system into two regions that are treated at different levels of theory:The smaller part directly involved in the electronic process is described using accurate quantum-chemical methods, while the effects of the rest of the system, the environment, are incorporated into the Hamiltonian of the quantum region in an effective manner. This thesis presents extensions of the PE model with theaim of expanding its range of applicability to describe electronic transitions in large molecular systemsin the optical and X-ray regions. The developments cover both improvements with regardto the quantum region as well as the embedding potential representing the environment.Regarding the former, a damped linear response formulation has been implemented to allow for calculations of absorption spectra of large molecular systems acrossthe entire frequency range. A special feature of this development is its abilityto address core excitations that are otherwise not easily accessible.Another important development presented in this thesis is the coupling of the PE model to a multi-configuration self-consistent-field description of the quantum region and its further combination with response theory. In essence, this extends the PE model to the study of electronic transitions in large systems that are prone to static correlation --- a situation that is frequently encountered in biological systems. In addition to the direct environmental effects on the electronic structure of the quantum region, another important component of the description of electronic transitions in large molecular systems is an accurate account of the indirect effects of the environment, i.e., the geometrical distortions in the quantum region imposed by the environment. In thisthesis we have taken the first step toward the inclusion of geometry distortions in the PE frameworkby formulating and implementing molecular gradients for the quantum region. To identify critical points related to the environment description, we perform a theoretical analysis of the PE model starting from a full quantum-mechanicaltreatment of a composite system. Based on this, we present strategies for an accurate yet efficient construction of the embedding potentialcovering both the calculation of ground state and transition properties. The accurate representation of the environment makes it possible to reduce the size of the quantum region without compromising the overall accuracy of the final results. This further enables use of highly accurate quantum-chemical methods despite their unfavorable scaling with the size of the system. Finally, some examples of applications will be presented to demonstrate how the PE model may be applied as a tool to gain insight into and rationalize the factors influencing electronic transitions in large molecular systems of increasing complexity.The dissertation was awarded the best PhD thesis prize 2016 by the Danish Academy of Natural Sciences.
QC 20170209
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Tegen, Stefan. « Einfluß der magnetischen Dipolkopplung auf den Tunnelmagnetowiderstand in Schichtsystemen und strukturierten Elementen ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2002. http://nbn-resolving.de/urn:nbn:de:swb:14-1014902838734-10106.
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We have studied the effect of the dipolar magnetic coupling (also known as Néel coupling or "orange-peel" coupling) in tunneling magnetoresistive (TMR) elements. With an in situ scanning tunneling microscope we directly accessed the roughness of the films and found a close correspondence between the values for the coupling fields determined by the magneto-optical Kerr effect and the ones computed on the basis of the measured morphology parameters. We confirm an increase of the dipole coupling between magnetic layers with decreasing barrier thickness as predicted by the model. Deviations from the theoretical predictions are observed for the case of thinner soft magnetic layers, which can be explained by reduced magnetisation in very thin films. We demonstrate the importance of dipolar coupling for understanding the magnetic behaviour of TMR elements by comparing TMR curves for optimised and nonoptimised structures.
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Tegen, Stefan. « Einfluß der magnetischen Dipolkopplung auf den Tunnelmagnetowiderstand in Schichtsystemen und strukturierten Elementen ». Doctoral thesis, Technische Universität Dresden, 2001. https://tud.qucosa.de/id/qucosa%3A24124.
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We have studied the effect of the dipolar magnetic coupling (also known as Néel coupling or "orange-peel" coupling) in tunneling magnetoresistive (TMR) elements. With an in situ scanning tunneling microscope we directly accessed the roughness of the films and found a close correspondence between the values for the coupling fields determined by the magneto-optical Kerr effect and the ones computed on the basis of the measured morphology parameters. We confirm an increase of the dipole coupling between magnetic layers with decreasing barrier thickness as predicted by the model. Deviations from the theoretical predictions are observed for the case of thinner soft magnetic layers, which can be explained by reduced magnetisation in very thin films. We demonstrate the importance of dipolar coupling for understanding the magnetic behaviour of TMR elements by comparing TMR curves for optimised and nonoptimised structures.
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Louis, Damien. « A new artificial spin system : the dipolar 4-state Potts model ». Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0154/document.
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Depuis la proposition en 2006 d’utiliser des nano aimants réalisés par des techniques top-down pour reproduire des « spins artificiels », l’étude des systèmes de spins artificiels a suscité un large intérêt. En effet la possibilité de pouvoir réaliser arbitrairement tous types de réseaux de spins artificiels et de pouvoir imager les configurations magnétiques de ceux-ci dans l’espace direct, offre un large terrain de jeu dans le domaine de la physique statistique. Jusqu’à présent seuls des réseaux de spins d’Ising, multi axes (réseaux kagomé ou carré avec une aimantation planaire) ou plus récemment uni axes (avec une anisotropie perpendiculaire), ont été étudiés. Cependant en physique statistique d’autres modèles de spins sont étudiés et notamment les modèles de Potts à q-états. Au cours de cette thèse nous avons étudié le cas d’un modèle de Potts à 4 états, ayant la particularité de posséder uniquement des interactions dipolaires entre les spins: le modèle de Potts dipolaire. Nous avons tout d’abord réalisé une étude théorique, montrant que sur un réseau carré, en fonction de l’angle entre les spins et ce réseau, le système possède des états fondamentaux très différents : un ordre antiferromagnétique, un ordre respectant les règles de la glace (2 in- 2 out) ou un ordre ferromagnétique. Dans une deuxième partie, nous avons exposé l’étude expérimentale du modèle de Potts dipolaire. Des réseaux formés d’aimants carrés ayant 300 nm de côté ont été réalisés par lithographie électronique, à partir d’une couche épitaxiée de Fer possédant une anisotropie quadratique. A température ambiante, ces plots possèdent une configuration magnétique monodomaine pouvant prendre 4 directions équivalentes, comme recherché pour le modèle de Potts dipolaire à 4 états. Un passage à 350°C (inférieure à la température de Curie) sous champ nul permet d’activer thermiquement la réorientation des spins afin qu’ils se rapprochent de l’état fondamental de l’assemblée de spins. Les configurations magnétiques observées après recuit, à l’aide d’un microscope à force magnétique, montrent l’importance du couplage dipolaire sur les états obtenus, ainsi que l’influence de l’angle entre les spins et l’axe du réseau. Les différentes configurations prédites théoriquement sont bien observéesSince the proposal in 2006 to use nanomagnets patterned by top-down techniques to mimic "artificial spins", the studies of artificial spin systems has attracted wide interest. As a matter of facts, the possibility to design "upon request" arbitrary network and the possibility to determine completely the "spin" configuration with magnetic imaging offer a wide playground for statistical physics. Up to now only Ising spin systems, multi axes with planar magnetization (on square or Kagome lattice) or more recently, single axis with perpendicular anisotropy, have been studied. However, beyond Ising spins, statistical physics and condensed matter physics have shown the interest of other spin models like q-state Potts models. In this thesis, we introduce the dipolar 4-state Potts model. It is shown that on a square lattice, depending on the angle between spins and lattice, the system present very different properties like antiferromagnetic order, spin ice state (2 in-2 out ice rule) and even dipolar ferromagnetism. This model has been realized experimentally. 300 nm square magnets are patterned from a 2 nm thick Fe layer with cubic anisotropy. At room temperature, the magnets present a uniform state with 4 equivalent directions. Upon heating at 350 °C the magnets switch from one direction to another. It is therefore possible to simply drive the system toward its ground state. The magnetic configurations determined by magnetic force microscopy reveals the importance of the dipolar coupling as the different expected ground states (antiferromagnetic, spin ice and ferromagnetic) are indeed observed. It is noticeable that these very different properties are obtained with the same "spins" (magnetic elements) and same lattice
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Höhr, Timm. « Dipolare Relaxationen in ungeordneten Systemen ». [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB8765356.
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Suzuki, Yohichi. « Free energy landscape of dipolar system : statistical and dynamical analysis ». 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136910.
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Kent-Dobias, Jaron P. « Energy-Driven Pattern Formation in Planar Dipole-Dipole Systems ». Scholarship @ Claremont, 2014. http://scholarship.claremont.edu/hmc_theses/66.
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A variety of two-dimensional fluid systems, known as dipole-mediated systems, exhibit a dipole-dipole interaction between their fluid constituents. The com- petition of this repulsive dipolar force with the cohesive fluid forces cause these systems to form intricate and patterned structures in their boundaries. In this thesis, we show that the microscopic details of any such system are irrelevant in the macroscopic limit and contribute only to a constant offset in the system’s energy. A numeric model is developed, and some important stable domain morphologies are characterized. Previously unresolved bifurcating branches are explored. Finally, by applying a random energy background to the numer- ics, we recover the smörgåsbord of diverse domain morphologies that are seen in experiment. We develop an empirical description of these domains and use it to demonstrate that the system's nondimensional parameter, which is the ratio of the line tension to the dipole–dipole density, can be extracted for any domain using only its shape.
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Maier, Peter Georg. « Ordnung in zweidimensionalen, dipolaren Ferromagneten ». [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969357931.
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Klugkist, Joost André. « Mechanisms for photonic switching in systems of strongly interacting dipoles ». [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2008. http://irs.ub.rug.nl/ppn/306046253.
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Kumari, Anita. « Design Issues in Magnetic Field Coupled Array : Clock Structure, Fabrication Defects and Dipolar Coupling ». Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3194.
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Even though silicon technology is dominant today, the physics (quantum electron tunneling effect), design (power dissipation, wire delays) and the manufacturing (lithography resolution) limitations of CMOS technology are pushed towards the scaling end. These issues motivated us towards a new paradigm that contributes to a continued advancement
in terms of performance, density, and cost. The magnetic field coupled computing (MFC) paradigm, which is one of the regimes where we leverage and utilize the neighbor interaction of the nanomagnets to order the single-domain magnetic cells to perform computational tasks. The most important and attractive features of this technology are: 1) room
temperature operation, which has been a limitation in electrostatic field coupled devices, 2) high density and nonetheless 3) low static power dissipation. It will be intriguing to address queries like, what are the challenges posed by the technology with such exotic features? Answer to such questions would become the focus of this doctoral research.
The fundamental problem with magnetic field coupled devices is the directional flow of information from input to output. In this work, we have proposed a novel spatially moving Landauer clock system for MFC nanomagnet array which has an advantage over existing adiabatic clock system. Extensive simulation studies were done to model and validate the clock for different length, size, and shape of nanomagnet array.
Another key challenge is the manufacturing defect, which leads to uncertainty and unreliability issues. We studied the different dominant types of geometric defects (missing material, missing cell, spacing, bulge, and merging) in array (used as interconnects) based on our fabrication experiments. We also studied effect of these defects on different segments (locations) of the array with spatially moving clock. The study concluded that a spatially moving clock scheme constitutes a robust MFC architecture as location of defect and length of arrays does not play any role in error masking as opposed to conventional
clock.
Finally, the work presents the study on the 2D nanomagnet array for boolean logic computation and vision logic computation. The effect of dipole-dipole interaction on magnetization state transition in closely spaced 2D array of ferromagnetic circular nanomagnet was explored. The detailed design space to demarcate the boundary between single domain state and vortex state reveals that the single domain state space is desirable for Boolean logic computation while the space around the boundary would be appropriate for vision logic computing.
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Moyses, Matthew. « Thermal vibrations and surface dipole moments for LEED from alkali adsorbate systems ». Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307750.
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Roach, Austin Hayes. « Floating coil position detection system for the Levitated Dipole Experiment ». Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32912.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 49-50).
The Levitated Dipole Experiment (LDX) is a joint Columbia University/MIT research collaboration sited at MIT's Plasma Science and Fusion Center. LDX is investigating the physics of a plasma confined in a dipole magnetic field. The field is created with a superconducting electromagnetic ring in the center of a large vacuum chamber. The goals of the experiment call for the ring to be levitated in the center of the vacuum vessel by the magnetic field of another superconducting electromagnet. This act requires a feedback mechanism to control the position of the ring in the vacuum vessel. This thesis presents a design for a position detection system to give position information to the feedback controller and digital filters to reduce the effect of noise in the position measurements.
by Austin Hayes Roach.
S.B.
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Gutöhrlein, Robin [Verfasser], et Jörg [Akademischer Betreuer] Main. « PT-symmetric dipolar Bose-Einstein condensates : embedding in a Hermitian system and higher-order exceptional points / Robin Gutöhrlein ; Betreuer : Jörg Main ». Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2017. http://d-nb.info/1138630799/34.
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Morales, Eduardo. « Spatio-temporal ECG analysis for localization of arrhythmias using precordial ECG leads and 128-lead system ». To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Roney, Alfred B. « Structure and dynamics of heterogeneous molecular systems ». [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001678.
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OLIVE, ENRICK. « Thermodynamique a l'equilibre et dynamique chaotique dans des systemes de boussoles en interaction dipolaire ». Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10268.
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Dans le cadre d'etude de systemes 2d ou les interactions dipolaires jouent un role important, nous avons construit des reseaux de boussoles sur lesquels les premieres observations ont montre la grande richesse d'etudes possibles. Les divers comportements observes montrent en effet de nombreuses analogies avec des systemes physiques reels. Deux etudes differentes ont ete menees sur ces systemes, experimentalement et en simulation numerique parallelement. Dans la premiere, on s'interesse aux comportements du reseau carre soumis a des effets de temperature, qui sont analyses par un modele simple dans le cadre de la thermodynamique a l'equilibre. Les effets d'anisotropie, resultant des termes multipolaires, conduisent aux notions de defauts et de longueur de lignes. Ces quantites permettent de mettre en evidence la transition entre une phase ordonnee et une phase desordonnee. Une description detaillee de cette transition permet de definir l'apparition d'une direction privilegiee (directeur) au passage de la temperature critique. On definit alors un parametre d'ordre qui est une mesure du peuplement du directeur. La seconde partie de ce travail s'attache a la dynamique individuelle de quelques boussoles en interaction. Le diagramme de phase des regimes dynamiques observes experimentalement est etabli pour deux boussoles avec de faibles frottements soumises a un champ tournant. Pour une dissipation plus elevee, une etude de la destabilisation des regimes periodiques vers des regimes chaotiques est menee. Les routes vers le chaos sont alors identifiees (cascades de doublements de periode) par des diagrammes de bifurcations, et le chaos est mis en evidence numeriquement par des sections de poincare des attracteurs etranges. Cette etude de la dynamique des boussoles se termine par quelques comportements observes et mesures pour une ligne de dix boussoles en interaction. Un scenario nouveau se dessine alors: l'intermittence. Les perspectives d'une etude plus detaillee sur la dynamique des reseaux sont alors tracees
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Tanyer, Fatma Muge. « Design Of Log-periodic Dipole Array Feed And Wide Band Reflector Antenna System ». Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605948/index.pdf.
Texte intégralRésumé :
The introduction of broadband systems to communication and radar technologies has demanded the design of broadband antennas. In this thesis, broadband log-periodic dipole antennas and reflector antennas are investigated. A dual polarized log-periodic dipole antenna and a reflector antenna are designed and analyzed within the frequency band of 0.4-18 GHz.
Basic theory and calculations about mutual coupling between the linear antenna elements are given. The currents at the bases of dipoles of the log-periodic antenna are found and these currents are used as inputs for the design of the reflector antenna. After the simulations made with MATLABÒand FORTRAN, a prototype single polarized log-periodic antenna is produced. Developments on the prototype antenna are performed, both to improve the electrical characteristics of the antenna and to make the final design realizable. After the performance of the single polarized log-periodic antenna is found satisfactory, dual polarized antenna is produced. Performances of both single and dual polarized log-periodic antennas are measured in the anechoic chamber at ASELSAN®
Inc. After the measurements of the antenna, using the currents at the bases of the dipoles, a reflector antenna is designed using &ldquo
MIR&rdquo
program written in FORTRAN, which is based on physical optics method. A method to calculate the aperture blockage of the reflector is developed. Simulation results of reflector antenna are given.
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Michael, Pratheek. « Simulation Studies on ECG Vector Dipole Extraction in Liquid Medium ». Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6625.
Texte intégralRésumé :
To circumvent some inherent problems in the conventional ECG, this research reinvestigates an ‘unassisted’ approach which enables ECG measurement without the placement of leads on the body. Employed in this research is a widely accepted assumption that the electrical activity of the heart may be represented, largely, by a 3-D time-varying current dipole (3D-CD). From the PhysioBank database, mECG and fECG data were obtained, and Singular Value Decomposition (SVD) was performed to estimate the time-varying Vector ECG dipole. To determine the sensing matrix responsible for transforming the activity of the 3D-CD into the potential distribution on the surface of the medium, the ECG vector dipole signals are used to excite a 3D-CD in water medium of a specific shape-containing-ellipsoid model(s) in COMSOL tool. The sensing matrix thereby estimated is then utilized to reconstruct the 3D-CD signals from the signals measured by the probes on the surface of the medium. Fairly low NRMSEs (Normalized Root-Mean-Squared Errors) are attained. The approach is also successfully extended to the case of two ellipsoids, one inside the other, representing a pregnant female subject. Low NRMSEs (Normalized Root-Mean-Squared Errors) are again observed.
33
Cottle, Amy. « Development of a SQUID magnetometry system for a cryogenic neutron electric dipole moment experiment ». Thesis, University of Oxford, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711932.
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Faria, Alencar José de. « Dissipação e ruído de dipolos magnéticos coletivamente acoplados a um circuito ressonante ». Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-31102008-085617/.
Texte intégralRésumé :
Estudamos o amortecimento radiativo e o ruído de spins de um material magnético acoplado a um circuito ressonante. O amortecimento radiativo em ressonância magnética é um fenômeno de dissipação, na qual a magnetização preparada após um pulso de Rabi sofre um decaimento até seu estado de equilíbrio. O material magnético perde energia através do seu acoplamento com o circuito ressonante, que deve estar sintonizado na freqüência de Larmor dos spins do material. Apesar deste fenômeno ter sido estudado há vários anos, nenhuma descrição quântica completa lhe foi dada. Apresentamos um modelo hamiltoniano quântico que descreve o amortecimento radiativo. Para isto usamos o método de equações de Langevin quânticas. Mostramos que além do amortecimento radiativo do material magnético, se o circuito está em um estado inicial coerente, a magnetização adquire um movimento complicado não-trivial. Usando as mesmas equações de Langevin, estudamos a influência da amostra no ruído do circuito ressonante. Calculamos a densidade espectral da corrente no caso em que todo o sistema está em equilíbrio térmico. Pudemos verifcar a efcácia do método comparando-o com estudos anteriores. Além disso, estudamos as alterações do ruído do circuito quando uma tensão oscilante externa é aplicada. Nesta situação surgem dois outros picos laterais ao pico central do espectro de absorção da amostra magnética. Isso leva a três depressões no espectro da corrente do circuito. Este efeito deve-se à separação dupla dos estados de energia dos spins. Comentamos sobre a analogia deste fenômeno com a fluorescência ressonante observada na Óptica Quântica.We study the radiation damping and the spin noise of a magnetic material coupled with a resonant circuit. Radiation damping in magnetic resonance is a dissipation phenomenon, where magnetization prepared after a Rabi pulse decays toward its equilibrium state. The magnetic sample loses its energy by the coupling with resonant circuit, that must be tuned in Larmor frequency of the sample spins. Even though this phenomenon had been studied many years ago, no full quantum description was done. We present a quantum Hamiltonian model, that explains the radiation damping. We use quantum Langevin equation method for this task. Beyond radiation damping, we show the magnetization acquires an unusual intrincate motion, if the circuit initial state is coherent. Using the same Langevin equation, we study the sample influence on the resonant circuit noise. We calculate the current spectral density in the case of thermal equilibrium of whole system. We can verify the method efectiveness, comparing former papers. Moreover we study modifcations in the circuit noise, if an external oscillating tension is applied. In this situation, other two peaks emerge in the central peak sidebands of the sample absorption spectrum. It leads to appear three dips in circuit current spectrum. This efect is due to the splitting of the spin energy states. We comment about the analogy between this phenomenon and the resonance fluorescence in Quantum Optics.
35
Weldon, Jonathan Andrew. « A DIRECTION FINDING SYSTEM USING LOG PERIODIC DIPOLE ANTENNAS IN A SPARSELY SAMPLED LINEAR ARRAY ». Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1278470572.
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Rodriguez, Rodriguez Marta. « Catalytic systems adapted to glycerol medium : applications in selective processes ». Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30007.
Texte intégralRésumé :
La grande quantité des solvants utilisés dans l'industrie chimique représente un des problèmes les plus importants à aborder, d'un point de vue environnemental ainsi qu'économique. Les solvants communément utilisés sont volatiles, toxiques, inflammables et/ou corrosifs, et leur substitution par des autres moins nocifs est un objectif primordiale dans un cadre de développement durable. Le glycérol se présente comme un candidat prometteur pour remplacer les solvants organiques conventionnels. Il est généré comme produit concomitant dans la production de biodiesel. En conséquence, la valorisation du glycérol est devenue un enjeu majeur. Ce composé possède des propriétés très intéressantes pour être utilisé comme solvant en catalyse, telles que son innocuité, haut point d'ébullition, pression de vapeur négligeable, capacité de solubilisation de composés organiques et inorganiques, faible miscibilité avec autres solvants organiques et également son faible coût. Cette Thèse à pour objectif développer des nouveaux systèmes catalytiques dans un milieu glycérol. En particulier, dans ce travail nous montrons comme le glycérol promue la stabilisation de nanoparticules de cuivre (I) capables de catalyser la réaction de Huisgen 1,3-dipolaire entre alcynes terminaux et azotures organiques (connu comme la réaction click), de façon très efficace à température ambiante. Dans ce solvant, cette réaction peut aussi être réalisée en absence de cuivre avec alcynes internes non activés, en travaillant sous activation microondes. L'utilisation du glycérol favorise la réaction par rapport à des autres solvants (incluant ceux qui sont protiques), probablement grâce à sa capacité pour former liaisons d'hydrogène, favorisant l'interaction avec l'irradiation microondes (et ainsi accélérant la réaction). Avec le propos d'étudier des transformations stéréosélectives, nous avons préparé des nouveaux ligands énantiopures dérivés du PTA (1,3,5-triaza-7-phosphaadamantane). Ces composés innovants ont été utilisés en réactions énantiosélectives comme l'addition asymétrique de B2pin2 à N-Boc-imines (Cu) ou encore la alpha-amination (Cu), ou encore comme organocatalyseur (réaction de Morita-Baylis- Hillman)Solvents are used in huge amounts in the chemical industry and this is one of the biggest problems to be solved not only from an environmental point of view, but also for economic reasons. The solvents commonly used in the industry are volatile, toxic, inflammable and/or corrosive; then, their replacement by others less harmful represents a crucial objective. Glycerol appears as a promising candidate to substitute the conventional organic solvents. It is produced in huge amounts as a waste in biodiesel industry. Consequently, the valorisation of glycerol becomes an important concern. This compound possesses very interesting properties to be used as solvent such as its non-toxicity, the wide range of temperature for its liquid state, negligible vapour pressure, capacity for solubilising organic and inorganic compounds, low miscibility with other organic solvents and also its low price. This Thesis deals with the development of new catalytic systems in glycerol medium. In particular, in this work we show how glycerol can facilitate the stabilisation of copper(I) nanoparticles that are able to catalyse the 1,3-dipolar Huisgen cycloaddition between terminal alkynes and organic azides (known as click reaction). The reaction proceeds at room temperature and it is very efficient. Moreover, this reaction can be carried out in the absence of copper using non-activated internal alkynes, working under microwave irradiation. Glycerol favours the process in comparison with other solvents (including protic ones), probably due to its ability to form hydrogen bonds, which favours the interaction with the microwave irradiation (accelerating the process). With the aim of studying stereoselective transformations, we have conceived new enantiopure ligands derived from PTA (1,3,5-triaza-7-phosphaadamantane). These innovative phosphines have been applied in enantioselective processes, such as pinacolboryl addition to N-Boc-imines (Cu) or alpha-amination (Cu), among others, or as organocatalyst (Morita-Baylis-Hillman reaction)
37
Fuhrmanek, Andreas. « From single to many atoms in a microscopic optical dipole trap ». Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00655970.
Texte intégralRésumé :
This thesis focuses on the manipulation of rubidium 87 atoms in a microscopic optical dipole trap. The experiments are performed in various regimes where the number of atoms in the microscopic trap ranges from exactly one atom to several thousands on average.The single atom regime allows us to calibrate the experimental setup. We use it a quantum bit, which state we can prepare and read out with efficiencies of 99.97% and 98.6%, respectively. When several atoms are loaded in the microscopic trap we observe a sub-Poissonian distribution of the number of atoms due to light-assisted collisions in the presence of near-resonant light. A study of these collisions in our particular case (microscopic trap) reveals extremely high loss rates approaching the theoretical Langevin limit. Finally, we demonstrate that the loading of the microscopic trap is more efficient when we superimpose on this trap a second macroscopic trap, which we use as an atom reservoir. This reservoir allows us to load the micro trap from the macro trap in the absence of any near-resonant light, thus avoiding light-assisted collisions.The loading of the micro trap from the macro trap leads to optimal initial conditions for forced evaporation towards Bose-Einstein condensation with about ten atoms only. After evaporation we reach phase-space densities approaching the degenerate regime.
38
Hansson, Annie. « Stark Spectroscopy, Lifetimes and Coherence Effects in Diatomic Molecular Systems ». Doctoral thesis, Stockholm : Department of Physics, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-650.
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Torquato, Ciro Augusto Paula. « Estudo do efeito de dipolos em arranjos de antenas adaptativas de sistemas de comunica??o DS-CDMA ». Universidade Federal do Rio Grande do Norte, 2003. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15253.
Texte intégralRésumé :
Made available in DSpace on 2014-12-17T14:55:20Z (GMT). No. of bitstreams: 1
CiroAPT.pdf: 942128 bytes, checksum: 56e26f87c283ff837ca5212f483b63ad (MD5)
Previous issue date: 2003-10-17This master dissertation introduces a study about some aspects that determine the aplication of adaptative arrays in DS-CDMA cellular systems. Some basics concepts and your evolution in the time about celular systems was detailed here, meanly the CDMA tecnique, specialy about spread-codes and funtionaly principies. Since this, the mobile radio enviroment, with your own caracteristcs, and the basics concepts about adaptive arrays, as powerfull spacial filter was aborded. Some adaptative algorithms was introduced too, these are integrants of the signals processing, and are answerable for weights update that influency directly in the radiation pattern of array. This study is based in a numerical analysis of adaptative array system behaviors related to the used antenna and array geometry types. All the simulations was done by Mathematica 4.0 software. The results for weights convergency, square mean error, gain, array pattern and supression capacity based the analisis made here, using RLS (supervisioned) and LSDRMTA (blind) algorithms
Esta disserta??o de mestrado vem trazer um estudo sobre alguns aspectos que influenciam na aplica??o de antenas adaptativas em sistemas celulares DS-CDMA (ou simplesmente CDMA). Foram detalhados alguns conceitos b?sicos a respeito do sistema celular e em geral, bem como sua evolu??o ao longo do tempo, dando ?nfase ? t?cnica CDMA, no que diz respeito aos c?digos de espalhamento e princ?pio de funcionamento. A partir disso, o ambiente de r?dio m?vel, com suas caracter?sticas peculiares, foi abordado, bem como os conceitos b?sicos em que se baseiam o sistema de antenas adaptativas com sua poderosa capacidade de filtragem espacial, capaz de reduzir significativamente o efeito de sinais indesejados. Tamb?m alguns algoritmos adaptativos foram discutidos, esses s?o integrantes do processamento dos sinais captados pelos arranjos, e s?o respons?veis pela atualiza??o dos pesos que de certa forma controlar?o o diagrama de radia??o do arranjo. Mais especificamente, esse trabalho fundamentou-se na an?lise, mediante simula??es computacionais, do comportamento do sistema de antenas adaptativas face ao tipo de antena e ao tipo (geometria) de arranjo empregados. Todas as simula??es foram feitas utilizando o software Mathematica 4.0. Os resultados para a converg?ncia dos pesos, erro m?dio quadr?tico, ganho, diagrama de radia??o e capacidade de supress?o foram as grandezas que basearam as an?lises aqui feitas, utilizando para isso, os algoritmos RLS (supervisionado) e LSDRMTA (cego)
40
Küchenmeister, Jens [Verfasser], et K. [Akademischer Betreuer] Busch. « Modeling of nano-photonic systems using the adaptive Fourier Modal Method and analytical dipole models / Jens Küchenmeister. Betreuer : K. Busch ». Karlsruhe : KIT-Bibliothek, 2012. http://d-nb.info/102976462X/34.
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Riauka, Nerijus. « Compact and broadband antenna system at UHF ». Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6319.
Texte intégralRésumé :
The aim of this research was to study a novel, broadband, low cost, low profile and a high-medium gain antenna in the UHF band. This has been achieved through numerical modelling, theoretical investigation and physical measurements. In this study two commercially available antenna systems are investigated in order to compare and establish potential deficiencies in the UHF antenna systems. A number of disadvantages are resolved within a novel antenna system design. The parametric study is performed for each element of the novel antenna system in order to optimise its overall performance. The indoor and outdoor measurements have been carried out in house, in order to validate the predicted results. The novel antenna system is compared to the most popular and commercially available UHF antenna systems. The study demonstrates that the novel antenna system has clear advantages such as broadband, balanced, compact and low cost when compared to the commercial antenna designs studied here. The comparison of the manufacturers' data to the measured results shows a good match, validating the outdoor measurements technique used in this research.
42
Hinder, Fabian Verfasser], Jörg [Akademischer Betreuer] [Pretz et Lutz Werner [Akademischer Betreuer] Feld. « Development of beam diagnostic systems for electric dipole moment measurements at particle accelerators / Fabian Hinder ; Jörg Johannes Pretz, Lutz Werner Feld ». Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1170680178/34.
Texte intégral
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Alcaraz, de la Osa Rodrigo. « Nanostructured systems with arbitrary electric and magnetic properties : Development and Application of an Extension of the Discrete Dipole Approximation (E-DDA) ». Doctoral thesis, Universidad de Cantabria, 2013. http://hdl.handle.net/10803/117776.
Texte intégralRésumé :
The discrete dipole approximation (DDA) has been successfully applied to many light scattering problems. Simply stated, the DDA is an approximation of the continuum target by a finite array of polarizable points. The points acquire dipole moments in response to thelocal fields. The dipoles of course interact with one another via their electric and magnetic fields, so the DDA is also sometimes referred to as the coupled dipole approximation. As of today, the method has established itself as one of the best solutions to calculate the scattering of radiation by particles of arbitrary shape. Hitherto, however, the main existing implementations include materials with relative magnetic permeability equal to 1 only, which is correct for all materials in the optical frequency range.
Nonetheless, materials with unusual optical properties have arisen recently. This includes the possibility of having both electric and magnetic anisotropic properties (bianisotropic materials) in the most general case. The situation where both the real part of the electric permittivity and the magnetic permeability are negative corresponds to what is known as "left-handed materials", or negative index materials (NIM), with unconventional properties such as negative refraction. The treatment of these materials with a method as contrasted as the DDA provides several advantages, apart from possibly being the only method available in many cases.
This PhD Thesis has explored nanostructured systems with arbitrary anisotropic optical properties (both electric and magnetic) by means of an Extension of the Discrete Dipole Approximation (E-DDA). During the development of this dissertation, a computational code (E-DDA code) has been implemented, able to produce comparative results with existing DDA codes, obtaining an excellent agreement.
After validation, the method was then applied to a wide range of materials and situations, making a special reference to its application to magneto-optical materials (with an antisymmetric electric permittivity tensor) and composite materials.
As a summary, the status of the E-DDA code is mature enough to be applied to very different configurations, making it a very useful, flexible and stable computational tool for calculating scattering and absorption of light by irregular particles, including anisotropic materials both electrically and magnetically at the same time in the most general case.La aproximación de dipolo discreto (o DDA por sus iniciales en inglés) ha sido empleada con éxito en multitud de aplicaciones dentro del ámbito de la difusión de luz. Básicamente consiste en discretizar el blanco difusor en elementos polarizables. Los elementos adquieren momentos dipolares en respuesta a los campos locales. Los dipolos por supuesto interaccionan entre ellos por medio de sus campos eléctricos y magnéticos, por eso a la DDA también se la conoce como aproximación de dipolo acoplado. A día de hoy, el método se afianza como una de las mejores soluciones para calcular la radiación difundida por partículas de forma arbitraria. Hasta ahora, sin embargo, las principales implementaciones existentes sólo incluyen materiales en los que la permeabilidad magnética relativa puede aproximarse por la unidad, lo cual es acertado para todos los materiales en el dominio de las frecuencias del rango óptico. No obstante, últimamente están apareciendo materiales con propiedades ópticas inusuales, como por ejemplo el caso de que algunas de sus constantes ópticas efectivas sean negativas (sus partes reales), o bien que presenten anisotropía tanto para el campo eléctrico como para el magnético (materiales bianisótropos). El caso doble negativo correspondería a lo que se ha venido en llamar “materiales zurdos”, o materiales con índice negativo, con propiedades sorprendentes como la refracción negativa. El tratamiento de estos materiales con un método tan bien contrastado como es el DDA presenta bastantes ventajas, aparte de que en muchos casos puede ser el único método disponible. Esta Tesis Doctoral ha explorado sistemas nanoestructurados con propiedades eléctricas y magnéticas anisótropas por medio de una Extensión de la Aproximación de Dipolo Discreto (E-DDA). Durante el desarrollo de esta tesis, se ha implementado un código computacional (código E-DDA), capaz de producir resultados comparativos con otros códigos DDA existentes, obteniendo un acuerdo excelente. Después de validarse, el método se ha aplicado a un amplio rango de materiales y situaciones, haciendo mención especial a su aplicación a materiales magneto-ópticos (con un tensor de permisividad eléctrica antisimétrico) y materiales compuestos. En resumen, el estado del código desarrollado es suficientemente maduro como para poder aplicarse a muchas configuraciones diferentes, haciendo de él una herramienta computacional útil, flexible y estable para calcular la difusión y absorción de luz por partículas irregulares, incluyendo materiales anisótropos tanto eléctricos como magnéticos en el caso más general.
44
Hinder, Fabian [Verfasser], Jörg [Akademischer Betreuer] Pretz et Lutz Werner [Akademischer Betreuer] Feld. « Development of beam diagnostic systems for electric dipole moment measurements at particle accelerators / Fabian Hinder ; Jörg Johannes Pretz, Lutz Werner Feld ». Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1170680178/34.
Texte intégral
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Perros, Sotirios Georgios. « The design and evaluation of transmit and receive antennas for an ionospheric communications probe system : A. Multiband Dipole Antenna ». Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23621.
Texte intégralRésumé :
Approved for public release; distribution is unlimitedThis thesis reports the design, performance evaluation and construction of a transmitting antenna for an HF communications probe system. A short range ionospheric communication link between Monterey, CA, (transmit site) and San Diego, CA, (receive site) was established to test the software and hardware of this probe system. The Multiband Dipole Antenna was selected as the more practical antenna for this link, using less real estate and support structure than other alternatives. The antenna was constructed and installed at the NPS beach site where the ground constants were measured accurately. Numerical Electromagnetics Code (NEC) analysis and measurements show that the antenna operates with low input VSWR ( < 1.5), is insensitive to electrical ground characteristics and has excellent radiation patterns for short range ionospheric communication links. Based on the observed signal strengths at San Diego, the antenna appears to be performing very well.
46
Katragadda, Mahesh. « Design and Simulation of a Planar Crossed-Dipole Global Navigation Satellite System (GNSS) Antenna in the L1 Frequency Band ». Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1345227397.
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Nestler, Franziska. « Efficient Computation of Electrostatic Interactions in Particle Systems Based on Nonequispaced Fast Fourier Transforms ». Universitätsverlag der Technischen Universität Chemnitz, 2017. https://monarch.qucosa.de/id/qucosa%3A23376.
Texte intégralRésumé :
The present thesis is dedicated to the efficient computation of electrostatic interactions in particle systems, which is of great importance in the field of molecular dynamics simulations. In order to compute the therefor required physical quantities with only O(N log N) arithmetic operations, so called particle-mesh methods make use of the well-known Ewald summation approach and the fast Fourier transform (FFT). Typically, such methods are able to handle systems of point charges subject to periodic boundary conditions in all spatial directions. However, periodicity is not always desired in all three dimensions and, moreover, also interactions to dipoles play an important role in many applications.
Within the scope of the present work, we consider the particle-particle NFFT method (P²NFFT), a particle-mesh approach based on the fast Fourier transform for nonequispaced data (NFFT). An extension of this method for mixed periodic as well as open boundary conditions is presented. Furthermore, the method is appropriately modified in order to treat particle systems containing both charges and dipoles. Consequently, an efficient algorithm for mixed charge-dipole systems, that additionally allows a unified handling of various types of periodic boundary conditions, is presented for the first time. Appropriate error estimates as well as parameter tuning strategies are developed and verified by numerical examples.Die vorliegende Arbeit widmet sich der Berechnung elektrostatischer Wechselwirkungen in Partikelsystemen, was beispielsweise im Bereich der molekulardynamischen Simulationen eine zentrale Rolle spielt. Um die dafür benötigten physikalischen Größen mit lediglich O(N log N) arithmetischen Operationen zu berechnen, nutzen sogenannte Teilchen-Gitter-Methoden die Ewald-Summation sowie die schnelle Fourier-Transformation (FFT). Typischerweise können derartige Verfahren Systeme von Punktladungen unter periodischen Randbedingungen in allen Raumrichtungen handhaben. Periodizität ist jedoch nicht immer bezüglich aller drei Dimensionen erwünscht. Des Weiteren spielen auch Wechselwirkungen zu Dipolen in vielen Anwendungen eine wichtige Rolle. Zentraler Gegenstand dieser Arbeit ist die Partikel-Partikel-NFFT Methode (P²NFFT), ein Teilchen-Gitter-Verfahren, welches auf der schnellen Fouriertransformation für nichtäquidistante Daten (NFFT) basiert. Eine Erweiterung dieses Verfahrens auf gemischt periodische sowie offene Randbedingungen wird vorgestellt. Außerdem wird die Methode für die Behandlung von Partikelsystemen, in denen sowohl Ladungen als auch Dipole vorliegen, angepasst. Somit wird erstmalig ein effizienter Algorithmus für gemischte Ladungs-Dipol-Systeme präsentiert, der zusätzlich die Behandlung sämtlicher Arten von Randbedingungen mit einem einheitlichen Zugang erlaubt. Entsprechende Fehlerabschätzungen sowie Strategien für die Parameterwahl werden entwickelt und anhand numerischer Beispiele verifiziert.
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Lehner, Maximilian Jacob. « Study and design of magnetic attitude control systems for nanosatellites ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Trouver le texte intégralRésumé :
The objective of this bachelor thesis was to display all the attitude and control systems (ACS) available for CubeSats and how magnetic ACS are the most convenient option in terms of volume. Precisely this project focused on the procedure, the design and the laws of physics that are behind the creation of a torque rod, a magnetic attitude and control system conceived for nanosatellites.
After discussing the magnetic laws, the different types of materials of the core, and the geometric parameters of the core and of the wire, all of which determine the operating area of the system, a theoretical model for a torque rod was devised.
This was done by using the models present in Niccolò Bellini’s master thesis “Magnetic actuators for nanosatellite attitude control”, 2014.
This bachelor thesis ended with the gathering of some experimental data on an embedded magnetorquer collected through a Helmholtz cage.
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Bentley, Grace Ann. « Neurophysiological Correlates of the Critical Bandwidth in the Human Auditory System ». BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5619.
Texte intégralRésumé :
The critical bandwidth (CBW) is an auditory phenomenon that has been used to study various aspects of auditory processing, including auditory masking, complex tone processing, and loudness perception. Although the psychoacoustic aspects of the CBW have been well studied, the underlying neurophysiology of the CBW has not been as thoroughly examined. The current study examined the neurophysiology of the CBW in young adults, as well as loudness perception in response to the CBW. Auditory stimuli consisting of complex tones of varying bandwidths were presented to 12 individuals (6 male and 6 female, ages 18-26 years). Complex tones were presented around center frequencies (CFs) of 250, 500, 1000, and 3000 Hz at bandwidths of 2, 5, 8, 10, 20, 50, 100, 200, 500, 1000, and 2000 Hz. Participants made loudness perception judgments while electroencephalography measured and recorded components of the event related potentials (ERPs) in response to the acoustic stimuli. Reaction time (RT) was recorded for each behavioral response, and the latencies of the N1, P2, C3, and C4 components of the ERPs were obtained. The results showed that RT increased with increasing bandwidth followed by a decrease in RT corresponding approximately with the CBW. This indicated that participants perceived a change in loudness at bandwidths greater than the CBW. Significant differences, p < .05, in RT were observed in bandwidths of 5 Hz and greater, although there was not complete consistency in this observation across all CFs and bandwidths. No significant critical band-like behavior amongst ERP latencies was observed. The results indicated that responses to acoustic stimuli originating in the superior temporal gyrus progressed to areas of higher neural function in the mid-temporal lobe. It was observed that each response must be processed temporally and independently to determine if a frequency difference is present for each stimulus. This observation is significant because this type of processing had not been identified prior to the current study.
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Ameri, K. Al, P. Hanson, N. Newell, J. Welker, K. Yu et A. Zain. « DESIGN OF A RACE CAR TELEMETERING SYSTEM ». International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/607539.
Texte intégralRésumé :
International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis student paper was produced as part of the team design competition in the University of Arizona course ECE 485, Radiowaves and Telemetry. It describes the design of a telemetering system for race cars. Auto Racing is an exciting sport where the winners are the ones able to optimize the balance between the driver’s skill and the racing teams technology. One of the main reasons for this excitement is that the main component, the race car, is traveling at extremely high speeds and constantly making quick maneuvers. To be able to do this continually, the car itself must be constantly monitored and possibly adjusted to insure proper maintenance and prevent damage. To allow for better monitoring of the car’s performance by the pit crew and other team members, a telemetering system has been designed, which facilitates the constant monitoring and evaluation of various aspects of the car. This telemetering system will provide a way for the speed, engine RPM, engine and engine compartment temperature, oil pressure, tire pressure, fuel level, and tire wear of the car to be measured, transmitted back to the pit, and presented in a way which it can be evaluated and utilized to increase the car’s performance and better its chances of winning the race. Furthermore, this system allows for the storing of the data for later reference and analysis.